Treatment of hydrocarbon oils



July 18, 1933. c. w. MacKAY TREATMENT OF HYDROCA-RBON OILS Filed May 19, 1930 Patented` Julyr- 18, 19733 UNITED "STATES PATENT OFFICE cHARLEsW. niAcxAY, OF TULSA, OKLAHOMA, AssI'GNoR'TO THE TEXAS COMPANY, or ,NEW YORK, N. Y., A CORPORATIONYOF DELAWARE Y l Y'rREAzriirErrr OF HYnROOARBON OILS Application med nay 19,Y 1930. serial No. 453,463.

This invention is concerned with the art lof Cracking hydrocarbon oils and has particular` reference; to certain novel and useful methods of withdrawing and handling the products of reaction, such as tar or residue,

from cracking vessels. i

Considerable diliculty has been experienced in withdrawing tar or residue `from cracking stills due particularly'to the formation of coke deposits in the lines through which it is sought to withdraw the residue.

In accordance .with my invention the prod-- ucts of reaction, as withdrawn from a crackmg vessel, are maintained 1n movement or circulation in such a way as to keep any coke or'carbon particles in suspension to thus facilitate the removal of the residue from the system and prevent the plugging up of lines.. The difficulties that have been encountered zo with respect to coke formations have been especially aggravating' whenVV it has been sought to pass the tar or residue directly to an expansion chamber, such as for autodistillation, since any expansion that may take place in lines or chambers is accompanied with a vaporizingaction tending to result in the deposition of cokeor carbon, and to overcome these diihculties myV invention has in View particularly the provision of circulating the tar or residue at points where expansion or reduction in pressure mayl take place. Y

The invention can best be explained by reference to a specific apparatus constituting an example of the invention and in order to more fully set forth theinvention reference .will now be had to the accompanying draw ing which is a diagrammatic sectional elevation of an apparatusconstructed in accorda ance with the invention and constituting an embodiment thereof.

In the apparatus thus illustrated a plurality of cracking stills 10 are indicated. It is to be understood that the invention is capable of being practiced in connection with a single cracking chamber or with any number of cracking chambers operated either in combination as a single unit or as separate and distinct units. Draw-off lines 11 are shown extending from the stills 10 to a common headt9 er Or tar line 12 which is provided with a presl riations in pressure that may occur due to sure reducing valve 13 and communicates with a vessel 14 which may function asa surge or; cushion drum. A drawol line 15 extends from the surge drum 14 to a pump 16 provided with a discharge line 17-which connects with the surge Vdrum so that thefcontents of the drum may be continuously maintained in circulation by the pump 16, drawing off` liquid from the drum 14 through the line 15 and rei turning it to vthe drum through the line 17 The line 17 is connected to a line 18 having a control valve 19 for the purpose of `permitting they withdrawal of a regulated quantity of theliquid in circulation through the surge drum 14 and fordelivering theliquid'thus withdrawnto a strippingV still 20. The strip` ping still is shownprovided with a residue draw-oline 21 and a vaponline 22 which extends toa dephlegmator or fractionating tow-V In` practicing the invention with the appay ratus illustrated the oil .is subjected to cracking temperatures under superatmospheric pressure inthe stills 10. Vhen distillation isl carriedon in the stills 10 the vapors are removed through means not shown and a residue isldeveloped in the stills which is withdrawn through the lines 11 to the tar header 12.' The drum 14 is operated at pressures intermediate those obtaining in the stills 10 and the stripping still 2li-,the pressure being reduced in the drum 14 bythe valve 13 and the Vpressure being reduced in the still 2O by" the valve 19. `The surge drum may serve to act as a cushion to absorb or takecareof va the taking of shots or drags from the stills 10 through the lines 11 and'to. facilitate the even delivery of a regulated amount of material to the stripping still 20, so that pressure fluctuations therein may be 'reduced to a minimum and an even distillation obtained. It'is to be understood that the relative'pressures Obtaining in the Vstills 10, surge drum 14, and stripping still 20 may be'varied within comparatively Widelimits but as an example of the invention it may be stated that with the stills 10 operatingunder about 400 pounds pressure, the pressure in the surge drum 14 may fluctuate, for instance, between 7 5 to `25() pounds pressure with an average pressure of about 200 pounds, and the pressure in the stripping still 2O may, for example, be approximately atmospheric or slightly higher.

The residue withdrawn from the stills 10 is thus expanded into the surge drum 14 and Y the pump 16 takes suction on the contents of ydrocarbon oils intolower boiling ones wherethe drum and pumps the material back through the line 17 to thus maintain the con-` tents of the drum in constant movement or circulation so that any coke formed'is held in suspension in the flowing oil. A regulated quantity of liquid ispermitted to be with-v drawnithrough the line 18 and valvef19 into the stripping still 20.v Distillation in the still 20A is carried on to the extent desired, which distillation maybe aided by Steam or other carrier gasl or heating means, if necessary. Thus the materialA delivered to the still 20 maybe distilled down to a fuel oil residiuum or to a pitch, which may be witlidrawn ina heated condition through the line 21, or the distillation my be carried on to the" extent of coking the residue. `The evolved -vapors are passed to thefractionating tower 23 which separates out a light vapor fraction which afterbeing condensed in the coil 25 is collected in the receiver 26. This condensate may, for example, be a gasdistillate. The reflux condensate formedk in the tower 23 may be' withdrawn through the line 27 and may be conducted to a cracking apparatus for further vcracking or otherwise utilized. Y

In a modification of the invention, in lieu of the4 surge drum 14;,a drum may be provided which is' connected, not only to the tar header 12, but also to vapor linesin com.- munication with the stills.r10,'so that this drum may be held under approximatelyv the pressure obtaining .in the cracking stills.

Due to the maintenance of still pressure 'onr this drum some post-cracking may take placeV in the drum and somecoolinginay take place. lBut as the coolingwhich mayftake place occurs while under approximately the pressure of the stillszthe tendency toward the formation of coke is minimized, while lthev circulation of the contents of the drum,

which is accomplishedin av simil'armanner'-` to the circulation carried on in the drum v1li,

which has been' specificallyA described, further prevents any clogging -up of linesthrough y:afname in the oil is subjected to cracking temperatui'es in a chamber-under superatmospheric pressure, the process that comprises withdrawing liquid from the cracking chamber, reducing the pressure on the withdrawn liquid and delivering it into a surge chamber` from which -novseparate Vapor fraction is Withdrawn and which is maintainedfat low-A er pressure than that of the cracking chamber, continuously withdrawing liquid from the surge chamber and passing it back to said chamber to thus create and maintain a circulation of the liquid delivered to said chamber, withdrawing from the liquid thus in circulation a regulated quantity of'liquid anddirecting it into a stripping still wherein distillation is carried on at lower pressure than that of the surge chamber. Y

2. Iii the conversion of higher boiling hy drocarbon oils into lower boiling ones whereina residue developed in the cracking of the oil under superatinosplieric pressure is removed froin thev cracking still and passed toa low pressure zone for autogeneousdistillav tion, the process that comprisesy withdrawing the residue from the crackingstill in a coii` fined stream and' delivering the residue, be-

chamber and passing it back to said chamber to thus establish and maintain a constant circulation of Vthe liquid tending `to maintain coke particles in suspension therein and withdrawing from-'the liquid thusY in cyclic move-V ment a regulated quantity th ereofiand directing the liquid thus withdrawn vto the `autodistillation Zone.

ciiAiinEsw. MGKAY. 

